For those with long memories, Delicious was one of the sites to use; it allowed people to bookmark their favourite websites for ease of access. At the time of founding, in 2003 Delicious was a real innovation, as the idea of being able to quickly and easily put stuff onto a third party website and then share that with your friends and colleagues was a really new idea. However, Delicious was unable to keep up with the times as other sites such as Diigo came along to give it real competition. It was sold several times - Yahoo paid between $15-$30,000,000 for it, but as usual with Yahoo! they really didn't know what they had and people began to migrate to other services, in particular Pinboard which has finally completed its victory, buying the ailing service for an astonishingly low $35,000.
If you're still a Delicious user then you will need to find yourself a new place to keep your bookmarks; I'd suggest Diigo if you want free, or you could go across to Pinboard and move your collection over, but it will cost you $11 a year for the privilege. Delicious will remain up for viewing, but you won't be able to add anything new. You can read more in the Pinboard blog entry, but in all honesty, you won't because you're not using Delicious any longer.
Shame to see it go, but it had outlived its purpose and was badly used by people who thought they had a cash cow on their hands.